<article id="wikiArticle">
<div></div>
<h2 id="Summary" name="Summary">概述</h2>
<p>该函数返回两个参数的类C的32位整数乘法运算的运算结果.</p>
<h2 id="语法">语法</h2>
<pre><code class="language-javascript"><code>Math.imul(a, b)</code></code></pre>
<h3 id="Parameters" name="Parameters">参数</h3>
<dl>
<dt><code>a</code></dt>
<dd>被乘数.</dd>
<dt><code>b</code></dt>
<dd>乘数.</dd>
</dl>
<h2 id="描述">描述</h2>
<p><code>Math.imul</code>可以进行快速的,类C语义的32位整数乘法.该特性对于一些项目比如<a class="external" href="http://en.wikipedia.org/wiki/Emscripten" rel="noopener" title="http://en.wikipedia.org/wiki/Emscripten">Emscripten</a>很有用.</p>
<h2 id="例子">例子</h2>
<pre><code  class="language-javascript">Math.imul(2, 4) // 8
Math.imul(-1, 8) // -8
Math.imul(-2, -2) // 4
Math.imul(0xffffffff, 5) //-5
Math.imul(0xfffffffe, 5) //-10
</code></pre>
<h2 id="Polyfill">Polyfill</h2>
<p>下面的JavaScript代码可以实现该函数:</p>
<pre><code  class="language-javascript">function imul(a, b)
{
        var ah  = (a &gt;&gt;&gt; 16) &amp; 0xffff;
        var al = a &amp; 0xffff;
        var bh  = (b &gt;&gt;&gt; 16) &amp; 0xffff;
        var bl = b &amp; 0xffff;
        // 右移0位可以修复高位的符号位
        return (al * bl) + (((ah*bl+al*bh)&lt;&lt;16)&gt;&gt;&gt;0);
}
</code></pre>
<h2 id="浏览器兼容性">浏览器兼容性</h2>
<p></p><div class="blockIndicator warning"><strong><a class="external" href="https://github.com/mdn/browser-compat-data" rel="noopener">We're converting our compatibility data into a machine-readable JSON format</a></strong>.
            This compatibility table still uses the old format,
            because we haven't yet converted the data it contains.
            <strong><a class="new" href="/zh-CN/docs/MDN/Contribute/Structures/Compatibility_tables" rel="nofollow">Find out how you can help!</a></strong></div>
<div class="htab">
<a id="AutoCompatibilityTable" name="AutoCompatibilityTable"></a>
<ul>
<li class="selected"><a>Desktop</a></li>
<li><a>Mobile</a></li>
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<div id="compat-desktop">
<table class="compat-table">
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<th>Feature</th>
<th>Firefox (Gecko)</th>
<th>Chrome</th>
<th>Internet Explorer</th>
<th>Opera</th>
<th>Safari</th>
</tr>
<tr>
<td>Basic support</td>
<td><a href="/en-US/Firefox/Releases/20" title="Released on 2013-04-02.">20</a> (20)</td>
<td><span style="color: rgb(255, 153, 0);" title="Compatibility unknown; please update this.">?</span></td>
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<th>Feature</th>
<th>Firefox Mobile (Gecko)</th>
<th>Android</th>
<th>IE Mobile</th>
<th>Opera Mobile</th>
<th>Safari Mobile</th>
</tr>
<tr>
<td>Basic support</td>
<td>20.0 (20)</td>
<td><span style="color: rgb(255, 153, 0);" title="Compatibility unknown; please update this.">?</span></td>
<td><span style="color: rgb(255, 153, 0);" title="Compatibility unknown; please update this.">?</span></td>
<td><span style="color: rgb(255, 153, 0);" title="Compatibility unknown; please update this.">?</span></td>
<td><span style="color: rgb(255, 153, 0);" title="Compatibility unknown; please update this.">?</span></td>
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<p> </p>
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